1. Field of the Invention
The present invention relates to a method for removing smear in a magnetoresistive (MR) effect element that a thin-film magnetic head includes for reading data. The invention also relates to a backup method of data using the removing method and a manufacturing method of a thin-film magnetic head using the removing method. Further, the present invention relates to a magnetic recording/reproducing apparatus with the function of removing smear.
2. Description of the Related Art
In recent years, with increase in capacity and reduction in size of magnetic recording/reproducing apparatuses, especially, magnetic disk drive apparatuses, higher sensitivity and larger output are required in thin-film magnetic heads. In order to respond to the requirement, a giant magnetoresistive (GMR) effect and a tunnel magnetoresistive (TMR) effect from which very high resistance-change rate can be expected are used for reading data. Thin-film magnetic heads provided with a current-perpendicular-to-plane (CPP) GMR effect elements or TMR effect elements having a CPP structure for high recording density is positively being developed.
The CPP structure is a structure which passes a sense current perpendicular to stacked surfaces of an MR effect multilayer which is a magneto-sensitive portion. In this structure, two shield layers sandwiching the MR effect multilayer therebetween play a role of electrodes. On the other hand, in a current-in-plane (CIP) GMR effect element and an anisotropic MR effect element having a conventional CIP structure, a sense current flows in the in-plane direction of the stacked surfaces of an MR effect multilayer. In this case, the two shield layers have to be insulated from the MR effect multilayer. Currently, narrowing of a read gap corresponding to high recording density easily causes an insulation failure between the shield layers and the MR effect multilayer in this CIP structure, which becomes a serious problem. On the contrary, in the CPP structure, the shield layers themselves are used as electrodes, and therefore, such a problem does not essentially occur. Therefore, the CPP structure is regarded as being more advantageous than the CIP structure in enhancement in recording density.
In the MR effect element having the CPP structure, occurrence of smear is one of the factors which reduce manufacture yield of thin-film magnetic heads. Polished marks (scars) remain on an air bearing surface (ABS) of a thin-film magnetic head or a head end surface on the ABS side on the occasion of polish as an MR height process step of a head manufacturing process. If the polished marks are formed to reach the end of the MR effect element reaching the head end surface on the ABS side, in some cases, a part of the end of the electrode layer (shield layer) or a part of the end of the MR effect multilayer may be trailed, and the inside of the MR effect multilayer or the MR effect multilayer and the electrode layer may be electrically short-circuited. The scar that causes the short-circuit becomes smear. Such smear has a possibility to cause substantial reduction in a sense current, and to bring about a defective of which read output does not satisfy the reference.
Further, smear can occur due to contact or crash of a thin-film magnetic head and a magnetic recording medium. Specifically, a scratch is formed on the ABS or the head end surface on the ABS side due to such contact or crash, and a part of the electrode layer end or a part of the end of the MR effect multilayer may be similarly trailed in some cases, and the inside of the MR effect multilayer or the MR effect multilayer and the electrode layer may be electrically short-circuited. The scar that causes the short-circuit also becomes smear. Such smear also has a possibility to cause substantial decrease in a sense current and to bring about an error of reduction in read output.
As a method for detecting the smear, for example, Japanese Patent Publication No. 2004-355740A discloses the technique of measuring the electric resistance value between an R+ or R− pad and an S pad provided on a slider (thin-film magnetic head), and determining that smear is present when the measured value is 1 kΩ or less. Further, as a machining process during manufacturing, which prevents occurrence of smear, Japanese Patent Publication 2004-249375A discloses lapping process which combines a main rocking motion and a subsidiary rocking motion. Further, as a machining process during manufacturing, which removes smear, Japanese Patent Publication No. 2000-242917A discloses the technique of removing smear by performing polishing with special slurry.
However, in these prior arts, smear that occurs during the use of a manufactured thin-film magnetic head cannot be removed. It is actually impossible to apply machining process as described above to a thin-film magnetic head provided within a magnetic recording/reproducing apparatus, and even if machining process is performed by taking out the head, the considerable number of process steps are required. Further, in the case of removing smear in the manufacturing process of a head, the smear is desired to be removed without going through the process which takes much time and effort and requires special adjustment as polishing disclosed in the above-described Japanese Patent Publication No. 2000-242917A.